The present invention relates to a method for transferring a conductive picture to an arbitrary surface of a detail by means of a printing means, an arrangement for transferring the conductive picture to the detail, a printing colour used for the conductive picture and printing pads used for the transferring of the printing colour. It also relates to a method for printing an electrical circuit pattern on a detail, e.g. a PCB, by using a printing pad, and an apparatus having at least one electrical component to be shielded from electromagnetic radiation.
It is previously known to transfer a predetermined picture to a surface by means of screen-printing or tampon printing. By means of these methods, it is also possible to print on slightly bulged surfaces. However, today""s printing technique imposes strong restrictions when it comes to printing on somewhat more complicated surfaces. Such surfaces can e.g. be very bulged, arched with small radii, angled and provided with angled corners, located adjacent to recesses, bumps, projections, protrusions and holes. There can also be surfaces, which are combinations of the above variations.
If the skilled person wants to print e.g. a conductive layer using today""s technique (spraying, vacuum metallization) on for example the inside of a mobile phone casing which has surfaces of the type described above, this will be very expensive, time consuming and still the result will be unsatisfactory since the printing colour (picture) will not cover the entire irregularities. It should be appreciated that printing of a conductive layer on a detail for shielding purposes, e.g. a mobile phone casing, is thoroughly discussed in the pending applications PCT/SE97/00372 and SE, 9801502-7, respectively, assigned to L M Ericsson, which applications are incorporated herein by reference. However, these applications are not explicitly related to the printing on irregularities of a detail, e.g. a mobile phone casing.
An object of the present invention is to eliminate this drawback and provide a method and an arrangement, which make it possible to print a determined conductive picture on the more complicated surfaces mentioned above.
Another object of the present invention is to form preferable printing pads which carry said conductive printing colour to the detail to be shielded.
Yet another object of the present invention is to create a conductive printing colour with appropriate thixotropy for applying on the detail to be shielded.
Yet another object of the invention is to overcome the drawbacks with the applying of an electrical circuit pattern on a printing circuit board (PCB) by conventional techniques, e.g. screen printing.
The above objects are achieved by means of a method, an arrangement, a printing pad and a printing colour.
The method and the arrangement according to the present invention describes the printing of a conductive picture on the surface of a detail by means of a printing means using a printing method known per se, wherein conductive partial pictures are printed on the surface of the detail so that every part of the conductive picture is built up step by step until the complete picture is achieved, wherein the conductive picture shields the detail from electromagnetic radiation.
By printing partial pictures on the surface of the detail rather than printing the complete picture in one printing, it is easier to cover all irregularities on the surface of the detail.
Another advantage is that the printing means can have a specific design for each particular irregularity to be printed with a partial picture. This increases of course the surface accessibility of the detail.
The printing pad prints a conductive picture containing a conductive colour on an irregular surface of a detail by means of a printing method known per se, wherein the pad fetches the conductive colour from a clichxc3xa9 and prints the colour on the detail, which colour shields the detail from electromagnetic radiation, and that the printing pad has a shape corresponding to the surface of the detail to be printed.
Since the pad has a shape corresponding to the detail to be printed, e.g. a mobile phone casing, it is easier for the colour to cover all irregularities of the detail. Moreover, the printing of the detail can be carried out in fewer steps.
The metal colour is included in the partial picture, which is to be printed on the surface of a detail by means of a printing means using a printing method known per se, which colour includes metal particles, an adhesive, a solvent, and an emulsifying agent in order to have an appropriate thixotropy and viscosity for adhering to a printing pad, preferably a silicon tampon pad.
In spite of the heavy weight of the metal colour, it adheres very well to a printing pad, preferably a silicon tampon pad, because of its inventive composition.
One method discloses the printing of an electrical circuit pattern containing metal colour on the surface of detail by means of a printing means using a printing method know per se, wherein the printing means fetches the electrical circuit pattern from a clichxc3xa9 and then print it on the detail.
The conventional techniques for applying circuit patterns on for example printing circuit boards (PCB) are very time consuming and expensive, e.g screen printing.
The method described above is a very simple and fast way of applying a circuit pattern on for example a PCB; fetching a circuit pattern from a clichxc3xa9 by means of a tampon pad and then printing the pattern on the PCB or a telephone casing. This method could readily be used in a very fast production line described below for manufacturing of phone casings or PCB""s applied with this electrical circuit pattern. Wider electrical lines, as for example power lines or antenna pattern lines, are particularly suitable for this method. The method could for example be used for printing the antenna pattern on the flip of the phone casing.
A short description of the independent claims and their advantages has now been carried out. Below, a brief discussion of advantageous embodiments of the dependent claims will now be discussed.
In one embodiment of the invention, the printing means prints the conductive partial pictures on the surface of the detail from different application angles for better surface accessibility of the irregularities.
Since the printing means is applied from different angles, the irregularities of the detail will be better covered by the printing colour.
In another embodiment, a rotating drive wheel carrying printing pads prints a conductive picture on details transported on a conveyor line, wherein the printing takes place under motion of both the detail on the conveyor band and the drive wheel. It should be realised that the detail and the printing pad in the above embodiments can be replaced by the mobile phone casing and the tampon pad, respectively.
Arrangement claims corresponding to the above embodiments could also be find in the appended set of claims.
Preferable shapes of the tampon pad corresponding to irregular surfaces of a phone casing are discussed in the dependent claims. The tampon pad could for example have an oval, axe, flat or pointed shape or even be cut in sections to be more pliable in the casing.
A preferable design of the clichxc3xa9 is suggested in the dependent claims, wherein the clichxc3xa9 at some areas of the surface have deep recesses to contain more colour. These areas correspond to irregular areas of the mobile phone casing needing more colour. Also a curved clichxc3xa9 is suggested in the dependent claims for facilitating for the tampon pad to absorb the colour.
An advantageous metal colour, which adheres readily on the tampon pad and on the casing, includes silver particles, copper particles or silver plaited copper particles.
Other characteristics of the invention are set out in other dependent claims.